Invited
Spontaneous and directed symmetry breaking in chiral nanocrystals

We have recently been working on handedness controlled synthesis of inorganic nanocrystals made of materials which crystallize in chiral space-groups. In the talk I will describe the demonstartion of strong chiral amplification in the colloidal synthesis of intrinsically chiral lanthanide phosphate nanocrystals, quantitatively measured via the circularly polarized luminescence of the lanthanide ions within the nanocrystals. We obtained 100% enantiomeric purity of the nanocrystals by using chiral tartaric acid molecules in the synthesis which act as an external “chiral field”, sensitively directing the amplified nanocrystal handedness through a discontinuous transition between left- and right-handed excess. The amplification involves also spontaneous symmetry breaking into either left- or right-handed nanocrystals below a critical temperature, in the abcense of the tartaric acid molecules. These characteristics suggest a conceptual framework for chiral amplification, based on the statistical thermodynamics of critical phenomena, which we use to quantitatively account for the observations. Our results demonstrate how chiral minerals with high enantiomeric excess could have grown locally in a primordial racemic aqueous environment.